The application claims the priority of Japanese Patent Applications No. 2003-368276 filed on Oct. 29, 2003 which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an electronic endoscope apparatus. In particular, it relates to a configuration of an electronic endoscope apparatus which forms a digital image of an object under observation based on an output signal from a solid state image pickup device mounted on an electronic scope and can store image data of the digital image on a recording medium.
2. Description of the Related Art
Electronic endoscope apparatus have a solid state image pickup device such as a CCD (Charge Coupled Device) mounted on the tip of an electronic scope (electronic endoscope). The CCD images an object under observation illuminated by light from a light source. When imaging signals obtained by the CCD are outputted to a processor unit and subjected to various video processing in the processor unit, it becomes possible to display images of the object under observation on a monitor, record still images and the like on a recording device, and so on.
As also described in Japanese Patent Laid-Open No. 2000-287203, electronic endoscope apparatus of this type perform not only analog processing for output to a regular NTSC (PAL) monitor, but also digital image processing to output images of the object under observation for use on various external digital devices such as a personal computer monitor.
In view of the recent tendency toward higher pixel counts and higher resolution of CCDs which are solid state image pickup devices, it has been proposed to form digital images by making effective use of image information obtained by a CCD with a high pixel count. Specifically, there are standards such as VGA (Video Graphics Array) specification of 640 (horizontal)×480 (vertical) pixels, XGA (EXtended Graphics Array) specification of 1024×768 pixels, and SXGA (Super XGA) specification of 1280×960 pixels which differ in display pixel counts. Personal computers and the like can form image signals compliant with such a standard and use them on external digital devices and the like. Recording media for use on such external devices to record and store endoscope image data include PC cards, SmartMedia (registered trademark) cards, CompactFlash (registered trademark) cards, and MO (magneto-optical) disks.
However, since increases in the pixel count and resolution of a CCD increase the size of each image (data volume per image) obtained by the CCD, increasing the time required to transmit the image data, if it is necessary to wait for a recording process to complete each time image data is recorded on a recording medium, endoscopy cannot be conducted smoothly.
After a current examination, if images of the finished examination can be redisplayed easily on a monitor and the like before a next examination (of a next patient) is started, it will be useful in checking the results of the finished examination and providing an explanation to the patient, resulting in improved usability. However, if the electronic scope is replaced by another one equipped with a solid state image pickup device with a different pixel count for examination of the next patient after the examination, the clock frequency for image processing may change. In such a case, if images of the finished examination are displayed again, display size on the screen may change, resulting in hard-to-view images.